A liquid crystal display device includes a lower substrate including a light blocking layer, a color filter, and an ITO pixel electrode; an active circuit portion including a liquid crystal layer, a thin film transistor, and a capacitor layer; and an upper substrate including an ITO pixel electrode.
The light blocking layer blocks uncontrolled light transmitted out of a transparent pixel electrode of a substrate and thus prevents contrast reduction due to light transmitted through a thin film transistor. Red, green and blue light blocking layers transmit light with a predetermined wavelength of white light and display colors.
The light blocking layer is generally fabricated using a pigment dispersion method. The pigment dispersion method includes coating a transparent substrate with a colorant-containing photopolymerizable composition, exposing the coating to provide a pattern by thermal curing, and removing non-exposed portions with a solvent.
High heat resistance may be obtained when a photosensitive polyimide or phenol-based resin is used as a binder resin in the pigment dispersion method. Sensitivity, however, may be lowered and an organic solvent is required as a development solvent.
A photoresist using an azide compound can also be used in a pigment-dispersion method. Such a photoresist, however, can have low sensitivity and heat resistance and may be affected by oxygen during exposure.
Acrylic-based resins can have good heat resistance, shrinkage-resistance, chemical resistance, and the like, but also can have reduced sensitivity, development property, and close contacting (adhesive) properties. In addition, a large amount of black pigment is typically included to adjust optical density of a light blocking layer, which can significantly deteriorate sensitivity, development properties, and close contacting properties.